/Engine/Source/Runtime/Slate/Public/Widgets/Layout/SExpandableArea.h
Constructs the header area widget
virtual [TSharedRef](API\Runtime\Core\Templates\TSharedRef)< [SWidget](API\Runtime\SlateCore\Widgets\SWidget) > ConstructHeaderWidget ( const [FArguments](API\Runtime\Slate\Widgets\Layout\SExpandableArea\FArguments) & InArgs, [TSharedRef](API\Runtime\Core\Templates\TSharedRef)< [SWidget](API\Runtime\SlateCore\Widgets\SWidget) > HeaderContent )